schema resolution?

[Yang <te...@gmail.com>]

now I rely on schema resolution to enable my server to move onto a
newer schema, while allowing clients to keeping using
old schemas for a while.

when the server moves onto a newer schema, if I do not change the
schema name, and hence the class name of the generated classes,
old clients think that they are seeing the same schema, so schema
resolution does not take place (correct me if I'm wrong here, but I
remember the rule for schema resolution to happen is that both package
name and class name must be the same).

so when I move to newer schema, I create a new package (namespace in
avro), and move the old schema into the new package ,

for example, I have

com.mycompany.v1.MyAvroRecord
                           .v2.MyAvroRecord
 ......

so every time I evolve, I just modify the schema, recompile. but I
have to modify all the "import" code in my server.


it would be easier if we modify the resolution triggering rule so that
every class has a serial number, and as long as serial number is
different, schema resolution is required. this way,server code does
not need to be modified with a new "import com.mycompany.v2.* " on
every schema version increase.

Thanks
Yang

Re: schema resolution?

[Yang <te...@gmail.com>]

never mind, please disregard the last email, the current code works fine.



I went through the code, it seems that "doc" is also compared . but
the doc says http://avro.apache.org/docs/1.5.1/spec.html#Schema+Resolution
"A schema's "doc" fields are ignored for the purposes of schema
resolution. Hence, the "doc" portion of a schema may be dropped at
serialization."

On Fri, Aug 19, 2011 at 4:49 PM, Yang <te...@gmail.com> wrote:
> now I rely on schema resolution to enable my server to move onto a
> newer schema, while allowing clients to keeping using
> old schemas for a while.
>
> when the server moves onto a newer schema, if I do not change the
> schema name, and hence the class name of the generated classes,
> old clients think that they are seeing the same schema, so schema
> resolution does not take place (correct me if I'm wrong here, but I
> remember the rule for schema resolution to happen is that both package
> name and class name must be the same).
>
> so when I move to newer schema, I create a new package (namespace in
> avro), and move the old schema into the new package ,
>
> for example, I have
>
> com.mycompany.v1.MyAvroRecord
>                           .v2.MyAvroRecord
>  ......
>
> so every time I evolve, I just modify the schema, recompile. but I
> have to modify all the "import" code in my server.
>
>
> it would be easier if we modify the resolution triggering rule so that
> every class has a serial number, and as long as serial number is
> different, schema resolution is required. this way,server code does
> not need to be modified with a new "import com.mycompany.v2.* " on
> every schema version increase.
>
> Thanks
> Yang
>